This mechanical method statement covers the excavation, installation, jointing and backfilling of underground coated carbon steel piping.
The pressure testing of all steel piping system will be conducted in accordance with applicable Hydrostatic Test Procedure.
Roles and Responsibilities
Project Manager is responsible for overall management including quality and HSE requirements of all construction activities at site including installation and testing of underground piping.
Piping Manager shall be responsible for overall management of piping activities. He shall be responsible for implementation of this procedure and shall pass the instruction down the line to maintain the required quality level.
All the piping engineers are responsible for planning and executing installation activities of underground piping at site and implementation of quality and HSE plans during construction works.
Piping Supervisors shall be responsible for requisitioning the materials required for installation, ensuring the installation as per approved drawings and implementation of good piping work and HSE work practices in their areas of operation.
Civil construction manager is responsible for the excavation and back filling of piping trenches, construction of concrete pits and all associated survey work.
QA/QC manager is responsible for overall management of QA/QC activities. He shall be responsible for non conformance management including quality audits both internal and external.
QC Engineer are responsible for QA/QC activities, material control and traceability, and review of test packages for hydro tests. He shall also be responsible for non conformance management and internal quality audits.
Quality control inspectors shall be responsible for carrying out inspection activities and witnessing NDE during the installation processes and coordinating with the clients QA/QC personnel for inspection and certification, as per approved ITP.
Safety officer shall be responsible for coordination with HSE authorities of owner safety officer shall monitor all the works to ensure that they are carried out correctly and in safe manner and advise supervisors for corrective measure, if required. He shall ensure that toolbox talks are held which shall cover details of specific tasks to the personnel and specific job risks involved are explained to the work force.
Health Safety & Environmental Requirements
The unsafe work practices and conditions in the work place shall be immediately identified and eliminated through the use of analytical techniques i.e. task specific risk assessment.
Build a team safety mentality where each worker contributes to the effort and each superintendent is fully aware of the capabilities and limitations of their team.
All tools and equipment’s shall be used in accordance with the manufacturer’s recommendations, required tool guards in place, and maintained in good working order.
Where appropriate, employees shall wear eye, ear, head, face and foot protection outfit.
Special care shall be taken for the erection of scaffolding and ladders at height.
When welder is welding, he shall wear the appropriate safety equipment and clothing to prevent him from getting an electric shock or burns.
A confined space entry permit is required before entry to confined space.
When welding in confined space, an extractor must be installed to remove hazardous / toxic fumes and to ventilate the area, if necessary a mask shall be worn and an assistant will be posted at the entrance to the work area in case of emergency.
When welding, inflammable materials must be removed from work area to avoid causing a fire.
Sequence of Work for Steel Pipe Installation
- Pipe transportation
- Excavation
- Wrapping (External)
- Pin hole test & Inspection
- Fabrication for spool and double joint pipe
- Internal cleaning and arrangement
- Fit-up and welding
- Rubber Lining (Welded Joints)
- Line leveling and supporting by sand bag
- Wrapping (Welded Joints)
- Pin hole test & Inspection
- Backfilling
- Hydrostatic test
Handling and Transportation
All coated pipes will be handled by means of wide sling bands or belts to avoid damaging the coating material.
Coated pipe shall be handled with wide nonabrasive canvas, leather belts and or other.
All equipment designed to prevent damage to the coating.
The use of tongs, bare pinch bars, chain slings, rope slings without canvas or composition belt slings with protruding rivets, pipe hooks without proper padding or any other handing equipment found to be damaging to the coating shall not be permitted.
All skid used to support coated pipe shall be padded.
Walking on the pipe shall not be permitted.
Excavation
Excavation by machine shall be carrying out if the working space is within the safe limit against the existing facilities.
Manual excavation shall be performed if the working area is to close to the existing underground facilities.
Shuttering or sheet piling (if required) should be done initially to ensure proper protection and stability of the existing facilities before commencing the excavation work.
Wrapping
Surface Preparation shall be according to Steel Structure Painting Council Specification SSPC-SP-3 (or equivalent).
Power Tool Cleaning SSPC-SP-2 (or equivalent), Hand Tool Cleaning may be used for narrow sections. Bare pipe shall be free from mud, mill scale, mill lacquer, wax coal tar, asphalt, oil, grease, or any other foreign materials. All prepared surface shall be coated on the same day it was cleaned. No pipe shall be allowed to flash rust before coating.
Liquid Adhesive (Primer) Application
Prior to any liquid Adhesive application, the pipe shall be cleaned to remove any wetness or other contamination. Liquid Adhesive shall be thoroughly agitated in its container before application to the pipe. Liquid adhesive shall be either brush or spray applied to the cleaned pipe surface in a uniform thin film at a minimum coverage of approximately 7.4 square meter per liter or Liquid Adhesive. Prime coat shall be dry to tacky at the time the anti-corrosion tape is applied.
Tape Installation
All irregular shaped items with voids shall be pre-coated with 2 inches wide of filler tape (mastic) such that smooth, rounded shapes are formed prior to application of anti-corrosion tape.
The anti-corrosion tape shall be applied directly onto the primed pipe surface by means of suitable mechanical wrapping equipment approved by the tape manufacturer in compliance with the applicable standard.
Anti-corrosion tape shall be spirally applied with minimum overlap of 55% of the tape width being used. The application tension on the tape shall be approximately 1% of tape width in width drawdown (approximately 5 to 10 lbs per inch width of tape).
Hand application is permitted only for tape width no wider than 6 inches. A tight, smooth, wrinkle-free coating should be observed throughout the application.
The end of each new roll of tape shall overlap the end of the preceding roll by a minimum of 6 inches. This end lap splice shall be hand applied for a wrinkle free splice to maintain the continuity of the anti-corrosion tape. The spiral angle of the new roll should parallel the previous roll’s spiral angle.
The outer-layer tape shall be applied over the anti-corrosion tape using the same method used to apply the anti-corrosion tape. The seam for the outer-layer tape shall overlap the exposed seam of the anti-corrosion tape by a distance of half the tape width so that they do not coincide. The overlap width shall be 1”. The application tension and the minimum end lap of two rolls shall be the same as the anti-corrosion tape. Additional outer-layer tape wrap with 1” overlap shall be applied for size over 50”.
Inspection and Testing
All coating shall be subject to 100% visual inspection and 100% inspection with an electrical holiday detector. The holiday detector shall be as per NACE RP-02-74 during the inspection of the anti-corrosion tape coating. Holiday detector shall not be permitted to remain stationary around coated pipeline with the operating voltage switched on. All defects shall be clearly marked.
All the defects in coating should be fixed immediately after the detection. Details of repair procedure shall be in accordance with Wrapping Procedure for Underground Piping.
String out the Pipes into Trench
Prior to the pipe string out, make sure that civil work for trench is complete.
Pipe joints will be laid individually in the trench on sand bags, suitable spaced to support the length of pipe being installed.
On long pipe lengths, sand bags will be spaced on five meter centers.
To avoid damage to the coating always follow the accepted construction practices.
Pipe will be installed in the trenches using wide sling belts and / or hands.
Tolerance of pipe laying shall be as follows:
Level of the pipe at any point along its length is to within ±15mm of the level stated on the drawings.
The center line of the pipe at any point along its length is to be within ±50mm of the location stated on the drawings.
While lowering the pipe into trench, pipe shall be inspected internally for dust / debris which, shall be cleaned (air blowing, brushing etc.)
Welding
Welding preparation, fit up, inspection and testing shall be carried out in accordance with project specification for piping fabrication by each service class.
All surfaces to be welded shall be free from oxides, scale, oil or other foreign matter.
Production joints shall be made using qualified welding procedures and welders.
Visual inspection shall be done by welding inspector during and after welding.
The daily welding report shall be generated by construction team in accordance with Welding Control Procedure.
Non Destructive Examination NDE
NDE shall be requested and carried out in accordance with method statement for NDE control.
All NDE requests shall be transmitted to subcontractor by QA/QC manager.
Contractor will transmit hard copies of NDE information to the client.
Matrix operator will input NDE date to the data base.
Repair of Welding: Welding repair shall be carried out in accordance with method statement for Welding Control Procedure.
Rubber Lining
Inspection for steel substrate: Size, appearance, welded parts and so on shall be checked and confirmed whether there are no defects, which may influence on lining work. If there are such defects, repair shall be performed.
Surface preparation shall be carried out by grinder on welding area, so that rust and scale on a steel surface are completely removed. In this process, welding areas shall be rechecked and if any defects, such as pinholes are found, repair shall be performed.
Bonding treatment: After grinded, first primer shall be immediately applied. After dried, rubber cement shall be applied and dried sufficiently.
Application of rubber sheet: Pre-cure rubber sheet (vulcanized rubber sheet : B-5S) shall be applied to steel substrate, so that no air bubbles are locked between rubber sheet and the surface of steel substrate.
Please refer to “Rubber Lining Procedure” below.
After lining application, following inspection shall be performed for whole rubber lined area.
(a) Thickness inspection
(b) Pinhole inspection
(c) Hardness inspection
(d) Appearance inspection
Backfilling Procedure
Backfilling work shall be carried out in accordance with Procedure for Earth Work.
Pipe padding should go after pipe bedding by filling with suitable materials 300mm thick from top of pipe.
Subsequently after completing the pipe padding backfilling of suitable excavated earth material shall be placed 300mm in layers and compacted in accordance with project specification requirements.
Hydro Test (Fire water system)
Epoxy coating shall be done at site.
Pipe surface shall be prepared by mechanical power tool cleaning.
Fit up and welding shall be carried out as per WPS.
Hydro test shall be carried out after completion of all NDE(if required) and spool clearance activities.
After completion of hydro test and its acceptance by owner, the epoxy coating of welded joints shall be done.
If any repair, modification occurs in the site during installation to the fabricated spool then the same spool shall be recoated and re-hydro tested in the site with the above same procedures.
The epoxy coating application shall be done in accordance with manufacturer’s instructions. Coating inspection shall be made and recorded on specific format.
Service Line Test
Before fit up and welding coating shall be removed from pipe in the range of 10cm over and the cut back area surface should be cleaned properly.
Pipe surface shall be prepared by mechanical power tool cleaning.
Fit up and welding shall be carried out as per approved WPS.
After completion of all NDE activities(if required), spool clearance shall be carried out epoxy and rubber coating.
Epoxy coating shall be done to all fabricated spools joints in the work shop.
The epoxy coating application shall be done in accordance with manufacturer’s instructions.
Field welding joints shall be coated at site as per manufacturer’s instructions. Coating inspection shall be made and recorded on approved format.
After installation of all spools at site and mechanical clearance of above lines by owner, the service test shall be done.
Holiday detection checks shall be carried out and recorded on forms.
As-built drawings must be drawn before leak test (As-built drawing shall be checked during punch check).
Testing
Preparation for testing
A punch list(will be attached in the Hydrostatic test procedure) shall be prepared by construction team to verify that the piping system are installed to the extent necessary for testing.
A test punch list shall be made through line check and punch list will be to verify that all piping components requiring post test actions are documented.
After all punch items are completed satisfactorily, both contractor and owner shall sign all necessary documents.
Pipe lines (FW line) shall be thoroughly blown out by air compressor.
Lines shall be free from all debris such as trash, welding rods, rags, tools, etc.
Test pack preparation and control
Preparation and control of test package shall be done in accordance with Hydrostatic Test Procedure.
All test package shall be approved by client prior to the start of pressure testing.
Main pressure testing
Every part that has to be tested should be vented until free of air.
Be aware that there is always a possibility of the presence of entrapped air in a system.
A hydrostatic pressure has to be built up gradually and, in doing so, no fast closing valves and booster pumps should be used.
All final inspection and documentation after pressure testing shall be done in accordance with method statement for pressure test of piping.
Service test line (Seawater, CCW etc.) shall be back filled after lapping & testing.
Records of pressure test and leak test shall include the following items.
- Date of test
- Identification of piping tested(line number and service)
- Test fluid
- Test pressure
- Certification by examiner
- Design pressure
- Photograph of pressure gauges and indication board showing the test sequence (time and pressure, etc.)
Repairing of Defects
When the defective material found during construction, a repairing method and extent shall be prepared.
Imperfections in welds exceeding specified limitations shall be considered as defects, removed and repaired in accordance with the followings.
(a) Defects shall be removed completely under the careful examination.
(b) Repair welding shall be also done in accordance with welding procedure specification(WPS)
Repaired welds shall be examined and inspected in accordance with Specification for Piping Fabrication by Each Service Class
Inspection and testing
All the work shall be inspected or examined as per approved ITP and inspection records shall be prepared as per ITP.
Before starting the job the drawings shall be checked for the latest revision.
All piping material & welding consumables shall be checked for conformity to specifications, construction drawings and approved WPS.
All measuring instruments shall be checked for valid calibration.
Area to be welded shall be checked for the cleanliness, free of paint, grease, dirt etc.
Each piping installation, including it’s components and workmanship, shall be examined to ensure compliance with applicable examination requirement.
Attachments
- Inspection and Testing Coat of Joint & Repairs
- Holiday Detector Test Report (HTR)
- Daily Welding and Inspection Record (DWIR)
- Job Safety & Environmental Analysis (JSEA)
Job Safety & Environmental Analysis (JSEA)
JSA should be used in conducting Tool Box Talks(TBT) with all concerned workers.
Make sure that all the necessary PPE are used, relevant PTW requirements are followed and all the control measures stated below are adhered to, the activity can proceed.
PPE & Safety Equipment Required to Perform Task (Select as Appropriate)
- Safety Helmet
- Face Shield
- Goggle
- Barricade
- Harness
- Hand Gloves
- Safety Shoes
- Ear Plug
- Coverall
- Safety Glasses
- Work Permit
- Fire Extinguisher
- Dust Mask
- Others
Sequence of Task: Mark out exact location of proposed excavation site, plus erection of barricades and safety signs.
Potential Hazards: Minor works only, no major hazards associated with this task.
Recommendations / Control Measures
► All works to be fully supervised at all times.
► If the supervisor has to leave the area, for any reason, then the job will be temporarily suspended until such time he returns to site.
► The excavation areas are to be identified on attached plot plan, highlighting the areas which can be excavated using machinery and the critical areas which must only be excavated by hand dig only.
Sequence of Task: Obtain excavation certificate including a hot work permit
Potential Hazards: For information only.
Recommendations / Control Measures
► Hot work permit to be issued by AOFP safety department.
Sequence of Task: Carry out excavation work using 360° mechanical excavator and hand digging operations as per attached plan.
Potential Hazards:
- Contact with moving machinery.
- Heat source from diesel powered equipment is a potential for explosion in the event of gas escape from live plant
- Earth sliding, cave-ins and collapse.
Recommendations / Control Measures
► Physical barricades shall be erected to prevent access by unauthorized personnel.
► Warning signs to be erected also to advise personnel of ongoing excavation work.
► Take all necessary precaution as required in confined space procedure when working in excavation or trench 1.5m or above.
► All excavated area should be barricaded by safety barrier and alerted by warning light at night.
► Proper slope should be maintained in all trench excavations (45deg slope is required or as per actual soil condition).
► Ladders, steps, ramps or other suitable means of access and aggress shall be provided as per procedure.
► Excavator operator and other related personals should be properly trained.
Sequence of Task: Pipe laying in the trench and fit-up
Potential Hazards:
- Tear of slings / belts
- Fall of materials
Recommendations / Control Measures
► All rigging area should be properly barricaded by suitable means.
► All riggers should be trained.
► Know the weight and C.G of the material to be lifted and use proper tools and equipment.
► All rigging tools and tackles should be checked before using.
► No one should stand beneath the load.
► Do not allow unauthorized persons in rigging premises.
Sequence of Task: Pressure testing
Potential Hazards:
- Equipment Failure
- Bursting, Leakage of test medium
- Damage to ear drum
- Heat stress and dehydration
Recommendations / Control Measures
► Ensure well maintained and periodic inspection of equipment & tools’
► Only trained personnel is required to handle the pressure testing equipment / tools.
► Ensure equipment is pre-mobbed and certified for use
► Prior to testing, ensure proper check on hose connections, blind points, bolting and on-line piping components and certified for test
► Ensure barriers / warning signs are in place around test areas and specify distance.
► Ear muffs must be worn at test area all time
► Ensure weather condition is conducive for work.
► Ensure availability of potable drinking water at work site and short break for workers.
Sequence of Task: Welding and Cutting works
Potential Hazards: Fire, explosion, damage to lives and properties
Recommendations / Control Measures
► Wearing of PPE shall be mandatory in all aspects of welding and cutting works.
► This shall include face shield and welding goggles.
► Hot work permit shall be secured prior to start of any welding and cutting works.
► Fire extinguishers shall be available near the work site at any time.
► Proper use of fire extinguishers shall be disseminated to all personnel involve in the job.
► All welding, grinding and cutting equipment shall be inspected prior to start.
► This shall also include inspection of electrical sources and cables.
► Damaged cables shall be immediately replaced.
► Only properly trained personnel shall be permitted to do welding and cutting works.
► Work area shall be properly barricaded.
► STAART required prior to start of task.
► Always check areas around and below prior to commencing welding or cutting operations.
► All combustible materials under or near welding or burning operations must be moved to a safe distance away or covered with a fire retardant material.
► Welding leads and gas hoses shall not be placed where they will present tripping hazards.
► Proper spark containment method such as fire blanket shall be used when doing welding and cutting.
► The welding machine shall be properly grounded and as close to the work as possible.
► Never leave a welding rod in the electric holder when not in use.
► Never use a torch as hammer to remove slag or scale. Use the proper tool.
► Never use lighters, matches or cigarettes to light a torch. Use only approved spark lighter.
► Welding machine shall be turned off at the end of the shift.
► Fire Blanket shall be used for welding habitat.
► All galvanized pipe shall be cleaned in areas to be welded prior to welding.
Sequence of Task: Grinding work
Potential Hazards: Injuries by grinding machine, Fire burn and eye injuries
Recommendations / Control Measures
► Only skilled worker can carry out the job.
► Avoid water contact and keep grinding machine always dry.
► Continuous training and remained hazard of grinding
► Damage of electric wire to be checked continuously.
► Grinding machine and grinding wheel should be checked before use
► Wear adequate PPE
Sequence of Task: Non Destructive Examination NDE
Potential Hazards: Exposure to X-ray
Recommendations / Control Measures
► Working area should protected by installing warning tape and x-ray hazard symbol.
► Only skilled worker can carry out the job
► Wear radioactive absorption batch when working to neutralized radioactive emission.
Sequence of Task: Housekeeping and area cleaning
Potential Hazards: Slip, Trip, Fall
Recommendations / Control Measures
► Proper housekeeping to be maintained at all times
► Material should never obstruct walkways / staircase / ladders and access to emergency equipment’s.
► Area to be cleaned and barricades and warning tapes to be removed
Sequence of Task: Handling of pressurize tanks (Oxygen, Acetylene, Argon)
Potential Hazards: Fire explosion damage lives and properties
Recommendations / Control Measures
► Hose and fittings of gas cylinders shall be checked for leak by soapy water.
► Oxygen and fuel gas cylinders in storage shall be separated by a minimum of 6 meters.
► Gas cylinders shall be handled carefully. Avoid bumping or dropping them.
► Always secure in an upright position and properly supported.
► Valve protection caps shall be on cylinders when not in use and when being transported.
► Be sure protective caps are adequately screwed down.
► Use a holding cage when lifting cylinders with a crane.
► Choking around cylinder shall not be allowed.
► Smoking is not allowed on the project site except in properly designated areas.
► Discard butts approved containers, not on the floor/ground or in trash cans.
Sequence of Task: General
Potential Hazards: All risks to be happened during working, Expected risks during night shift
Recommendations / Control Measures
► Every day before start of work tool box meeting to be between supervisor and worker.
► Supervisor should give information regarding hazards indulged to daily work activities.
► Always keep clean working area.
► Close supervision shall be done during late night hours.
► Supervisor should give information regarding hazards indulged to daily night work activities.
► Adequate drinking water facilities should be provided.
► Every night before start of work tool box meeting to be between supervisor and worker
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